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Description

11/5/13
LECTURE 19
Concept 1.2: The Core Theme: Evolution accounts for the unity and diversity of life
Taxonomy is the branch of biology that names and classifies species into groups of
increasing breadth
- Domains, followed by kingdoms are the broadest units of classification
- Species are the smallest
- Approximately 1.8 million species have been identified and named to date, and
thousands more are identified each year
The Three Domains of Life
Fig 1:13
Domain Bacteria, Domain Archaea comprise of the prokaryotes
- Prokaryotes are single-celled and microscopic
- Filamentous forms include cyanobacteria
Domain Eukarya
- Plants, which produce their own food by photosynthesis
- Fungi, which absorb nutrients
- Animals, which ingest their food 11/5/13
Unity in the Diversity of Life
Fig 1:14
A striking unity underlies the diversity of life
- DNA is the universal genetic language common to all organisms
- Unity (similarity) is evident in many features of cell structure
Charles Darwin and the Theory of Natural Selection
Charles Darwin published On the Origin of Species by Means of Natural Selection in 1859
Darwin made two main points
- Species showed evidence of descent with modification from common ancestors
- Via natural selection
Darwins Descent with Modification
- Traits in individuals in population vary, many are inheritable
- More offspring are produced than survive, competition is inevitable
- Species generally suit (adapt to) their environment
o Fig 1:18 Lightest colored beetles less likely to survive predation since easily
seen; darker grey beetles survive and thrive
Natural selection results in the adaptation of organisms to their environment
For example, bat wings are an example of adaptation:
- Unity same bones, joints, nerves etc. as human arm, foreleg of horse and flipper of
whale
- Diversity mammalian forelimbs results from modification by natural selection
operating over millions of generations
Descent with modification: adaptive radiation of finches on Galapagos Islands
Fig 1:2011/5/13
Jean Baptiste de Lamarck (1744-1829)
His hypothesis: nature is controlled by 3 biological laws:
1. Environmental influence (physical, chemical, in the womb) on organ development;
innate need to become more complex naturally
2. Use and disuse of parts: Parts of body used extensively get larger and stronger,
while other deteriorate e.g. stretching of the giraffes neck (intermediate giraffes?)
3. Inheritance of those modifications to next generation
Experiments showed that traits acquired by use/disuse during an individuals life were not
inherited.
Concept 22.2- Charles Darwin: Origin of the Species by Natural S